The present invention relates to engine starter gearing for an engine and more particularly to engine starter gearing of the positive shift type including a primary dentil clutch to provide driving and overrunning, a device for effecting the automatic separation of the clutch teeth after the engine becomes self-running, and a secondary or overload dentil clutch to absorb excess loads.
Various designs for engine starter gearing have been offered in the past in an effort to accommodate the various operating conditions experienced by engine starter gearing. However, the increasing tendency towards size and weight reduction in all accessories used in association with motor vehicles has resulted in design compromises affecting the performance of the engine starter gearing and its ability to handle unusual load conditions. In particular, many current engine starters experience failure during the extremely high loads which occur, for example, during an engine backfire or preignition condition. Under conditions of extreme load or frequent repetitions of moderate load, the armature shaft of the engine starter gearing may bend or break. Accordingly, what is needed is an overload device to absord or distribute the high load which may otherwise cause damage.
Various designs for engine starter gearing have been offered in the past to compensate for the extreme loads experienced during a backfire or a preignition condition. Examples of such designs may be found in U.S. Pat. No. 2,546,954, issued Mar. 27, 1951 to Tobias; U.S. Pat. No. 2,643,548, issued June 30, 1953 to Miller; U.S. Pat. No. 2,782,643, issued Feb. 27, 1957 to Miller; U.S. Pat. No. 2,815,669, issued Dec. 10, 1957 to Mendenhall; U.S. Pat. No. 2,880,619, issued Apr. 7, 1959 to Digby; U.S. Pat. No. 2,885,894, issued May 12, 1959 to Mendenhall; and U.S. Pat. No. 2,938,391, issued May 31, 1960 to Buxton.
While engine starter gearing made according to the teachings of many of these prior patents function well in terms of the absorption of certain shock loads experienced by the engine starter gearing, those prior art designs which function well for that purpose have a tremendous number of parts which results in a large and heavy engine starter assembly which is difficult to assemble.
Accordingly, what is needed is a simple, lightweight, and compact design for engine starter gearing having the capability of absorbing, without damage, such sudden torsional shock loads.